Cut the pork fillet into four pieces and place in a shallow non-metallic dish. Mix together the hoisin sauce with 15ml (1tbsp) of the oil and spread over the pork fillet. Cover and leave to marinate for 1 hr. Preheat the oven to 190°C (375°F, gas mark 5).
Place the pork on a wire rack set over a shallow roasting tin half-filled with water (this helps to keep the pork moist during cooking). Roast for 45-55 mins until the pork is cooked through and lightly charred in places.
Meanwhile, cook the rice according to the packet instructions. Drain well. Heat the rest of the oil in a frying pan and fry the chopped spring onion for 2-3 mins. Add the rice and cook for a further min. Slice the pork fillet and serve on the rice, garnished with shredded spring onion.